1. Field of the Invention
The present invention relates generally to a charging apparatus and method, and in particular, to a method for wireless charging using a communication network.
2. Description of the Related Art
A mobile terminal, such as a cellular phone or a Personal Digital Assistant (PDA), is powered by a rechargeable battery according to characteristics of the mobile terminal, and in order to charge the battery, electrical energy is supplied by a separate charger. Separate contact terminals are commonly equipped in a charger and a battery, and these respective contact terminals are placed into contact with each other, thereby connecting the charger and the battery to each other in order to charge the battery.
However, since such contact terminals protrude outwards, the contact terminals are easily contaminated due to foreign substances, thereby preventing the battery from being correctly charged. In addition, when the contact terminals are exposed to humidity, charging may not be performed correctly.
To solve these problems, wireless and contactless charging technologies have been recently developed and utilized to a number of electronic devices.
The wireless charging technology uses a wireless power transmission and reception system, for example, a system for automatically charging a battery only if a cellular phone is put on a charging pad without connecting the cellular phone to a separate charging connector. Such wireless charging technology is applied in wireless electric toothbrushes and wireless electric shavers, for example. Since the wireless charging technology can increase the effectiveness of a waterproof feature by charging an electronic product in a wireless manner and does not need a wired charger, the portability of the electronic product can be increased.
The wireless charging technologies are largely classified into an electromagnetic induction method using a coil, a resonance method, and a Radio Frequency (RF)/microwave radiation method for converting electrical energy to a microwave and radiating the microwave.
Although the electromagnetic induction method is currently the most widely used method, there have been recent success in experiments for transmitting power in a wireless manner at a distance of tens meters by using a microwave.
The electromagnetic induction method for transmitting power delivers power between a primary coil and a secondary coil. An induction current is generated when a magnet moves through a coil. A transmission end generates a magnetic field using the induction current, and a reception end generates energy by acting as a magnet. This phenomenon is referred to as a magnetic induction phenomenon, and a power transmission method using the magnetic induction phenomenon provides excellent energy transfer efficiency.
The electromagnetic induction method is a most practically used method and is applied to various devices. The conventional wireless charging or contactless charging technologies mostly uses the electromagnetic induction method, which is applied to products, such as electric shavers and toothbrushes, using a nickel battery.
For the resonance method, professor Soljacic at the Massachusetts Institute of Technology (MIT) announced in 2005 a system for wirelessly transferring electricity several meters from a charger using a coupled mode theory as the resonance type power transmission principle. This resonance method is based upon the concept that when a tuning fork is rung, a nearby wine glass also vibrates with the same number of vibrations as the tuning fork. The MIT team used resonance of an electromagnetic wave containing electrical energy instead of resonance of the sound. Unlike other electronic waves, since the electrical energy is directly transferred to a device having a resonance frequency only if the device exists nearby and an unused portion is reabsorbed into an electromagnetic field without being spread to the air, the electromagnetic wave according to the resonance method will not affect a nearby machine or human body.
The RF/microwave radiation method is a new concept of power transmission method for converting power energy to a microwave advantageous to wireless transmission to transfer the power energy. According to this method, electrical energy is transferred instead of a signal used in a wireless communication method for a radio or wireless phone. While general communication relates to a method of carrying a signal on a carrier, wireless power transmission relates to a method of transferring only a carrier itself.
Although the conventional wireless charging technology is generally limited to devices such as electric shavers and electric toothbrushes, recently, the resonance method has been developed and many researches has been proceeding to introduce the wireless charging technology to cellular phones and televisions. Accordingly, a method for helping power charging between devices capable of power transmission and reception has been being researched.